The ratchet device is widely used in hand tools, such as ratchet screwdriver, socket wrench, etc. As shown in FIGS. 1A, 1B, and 1C, a ratchet device of the prior art comprises a control body 10 which is connected with a tool handle and is provided with two arresting blocks 12A and 12A, each having a spring 11. The prior art ratchet device further comprises a ratchet main body 13 with a plurality of teeth 14. The ratchet main body 13 is fastened with a blade of the tool such that the teeth 14 are engageable with the arresting blocks 12A and 12B. The two arresting blocks 12A and 12B are engaged with the teeth 14, as shown in FIG. 1A. When the second arresting block 12B is caused by a ratchet shifter to become disengaged with the teeth 14, as shown in FIG. 2B, the control body 10 depends on the first arresting block 12A to allow the ratchet main body 13 to turn clockwise. As the control body 10 is turned in reverse, the teeth 14 of the ratchet main body 13 force out the first arresting block 12A which is thus disengaged with the first arresting block 12A, as shown in FIG. 1C. Meanwhile, the control body 10 can depend on the second arresting block 12B to allow a counterclockwise rotation of the ratchet main body 13. Similarly, as the control body 10 is turned in reverse, the second arresting block 12B is forced out by the teeth 14 of the ratchet main body 13. The prior art ratchet device described above is structurally deficient. As shown in FIGS. 2A and 2B, there is a gap between the control body 10 and the ratchet main body 13. In light of the gap, the control body 10 tends to move aside when the control body 10 is turned. As a result, the first arresting block 12A is not fully engaged with the teeth 14. Such a partial engagement of the first arresting block 12A with the teeth 14 results in an insufficient torsion. The same is true with the second arresting block 12B, as illustrated in FIG. 2B.
As shown in FIG. 3A, the tooth number of the teeth 14 of the ratchet main body 13 is twenty. As the control body 10 is turned in reverse, the control body 10 is turned in reverse an angle of 18 degrees, so as to move from one tooth 14 to another tooth 14. It is therefore apparent that the ratcheting stroke is limited in a confined space of thirty degrees. If the tooth number of the teeth 14 of the racket main body 13 is increased from 20 to 30, as illustrated in FIG. 3B, the control body 10 can move past two teeth (24 degrees) in the confined space of 30 degrees when the control body 10 is turned in reverse for an angle of 12 degrees. As a result, the ratcheting stroke is relatively increased. However, the depth of notches of the teeth 14 of the ratchet main body 13 becomes relatively shallow as a result of an increase in number of the teeth 14. It is readily conceivable that the first arresting block 12A does not engage securely with the shallow notches of the toothed ratchet main body 13. In another words, the first arresting block 12A is vulnerable to disengagement with the shallow notches of the teeth 14, as illustrated in FIG. 3C.
As shown in FIGS. 4A, 4B, and 4C, the Taiwan Patent Serial Number 88218399 discloses a ratchet screwdriver comprising a control body 20 and a ratchet body 23 with teeth 24. The control body 20 is provided therein with two arresting blocks 21A and 21B, which are confined by means of an elastic coil 22. The two arresting blocks 21A and 21B are engageable with the teeth 24 of the ratchet body 23. The control body 20 is further provided with a shifter 25 having a shifting block 26. In operation, only one arresting block is engaged with the toothed ratchet body 23. As a result, this prior art ratchet screwdriver is incapable of providing a sufficient torsion to bring about rotation of a screw which is securely fastened onto an object.
As shown in FIGS. 5A, 5B, and 5C, the Taiwan Patent Serial Number 91220384 discloses a ratchet handle structure comprising a control body 30 and a ratchet body 33 with teeth 34. The control body 30 is provided with two rotatable arresting blocks 31A and 31B, which are urged by a spring 32. The two arresting blocks 31A and 31B are engageable with the teeth 34 of the ratchet body 33 and are controlled by a shifter by which the arresting blocks 31A and 31B can be caused to disengage the teeth 34. In operation, only one arresting block is engaged with the toothed ratchet body 33. As a result, the ratchet handle structure is ineffective in providing a sufficient torsion.